When the toxicity of a chemical is evaluated by using an alga, it is necessary to prepare algal cells by carrying out a primary culture and a successive culture of cells maintained in a liquid culture or on an agar culture medium, and then to carry out the test by adding the test substance to the prepared algal cells. However, it is troublesome and inconvenient to maintain algal cells and to carry out the successive culture for each test.
To resolve this troublesomeness, it is possible to use frozen algal cells (Non Patent Literatures 1 and 2, for example). By thawing the frozen algal cells immediately before the test and using the thawed algal cells, it is possible to rapidly provide the algal cells for the test without carrying out the successive culture of the algal cells.